Calcuate Elastic Modulus of metal cable

[EroAlchemist]

Homework Statement

A mass of 225 kg is hung from a metal cable of length 1.60m and diameter 8.20mm. This causes the cable to stretch by an amount 0.668mm. Calculate the Elastic Modulus of the metal.

Homework Equations

E=(F/A)/(change L / orig L)

The Attempt at a Solution

F = mg = 2205N
A = Pi (r2) = 5.28*10^-5 m2
F/A = 2.2*10^7

Change L = 6.68*10^-4m
Orig L = 1.6m
CL/OL = 4.18*10^-5

(2.2*10^7) / (4.18*10^-5) = 5.26 *10^11 N/M2 = E

The book says the correct value for E = 100*10^9 N/M2. I'm not sure where I went wrong.
Thanks for the help!

 

[PhanthomJay]

Oh you have a couple of math or decimal point errors. Your formula is correct. Just recheck the math, it is easy to slip a decimal point or 2 when dealing with decimals or numbers with a lot of 000000000's

And welcome to PF!

 

[EroAlchemist]

Thanks - I'll check them again.
:)